ReefGIS :: Dataset Definitions
Coral Bleaching & SST
Coral Bleaching
High
Medium
Low
No Bleaching
Severity Unknown
Coral bleaching is a major phenomon affecting coral reefs around the world. An initial database of bleaching observations was compiled by UNEP-WCMC using a variety of sources. This database has been expanded by Dr. J. Oliver and Mr. Y. Yusuf from The WorldFish Center, using information from the ReefBase database, the Great Barrier Reef Marine Park Authority (GBRMPA), the CoralList, and other sources of information. This dataset also includes observations indicating no bleaching. You can add your observations of coral bleaching (or no bleaching) via our Bleaching Report.
NOAA Sea Surface Temperature
The sea surface temperature (SST) data available here in the ReefBase GIS are the means and maxima of SST for each month and year. They were derived from NOAA Coral Reef Watch (CRW) operational twice-weekly near-real-time global satellite nighttime sea surface temperature (SST) at 0.5 by 0.5 degree (~50 km) spatial resolution. The data come from AVHRR (Advanced Very High Resolution Radiometers) on board NOAA's Polar-Orbiting Operational Environmental Satellites (POES). Detailed information on the twice-weekly near-real-time SST is available at CRW's SST website.
NOAA Sea Surface Temperature Anomaly
The SST anomaly data presented here are the monthly and annual means, and the annual minimum and maximum value of NOAA CRW's operational twice-weekly near-real-time global satellite nighttime SST anomalies at 0.5 by 0.5 degree (~50 km) spatial resolution. The SST anomaly is the difference between CRW's nighttime SST and the SST climatology for the corresponding period. CRW's SST anomaly product makes it possible to quickly pinpoint regions of elevated and/or depressed SST across the world's oceans. It is especially valuable for the tropical regions where most of the world's coral reef ecosystems thrive. It is also very useful in monitoring ENSO (El Niño-Southern Oscillation) development, hurricane "wake" cooling, and even major shifts in coastal upwellings. Detailed information on the twice-weekly near-real-time SST anomaly is available at CRW's SST anomaly website.
NOAA Bleaching HotSpot
NOAA CRW's monthly and annual maximum bleaching HotSpots displayed in this GIS system outline the areas where the SST exceeds the temperatures corals would normally experience in the hottest month. Corals are vulnerable to bleaching in these anomalous areas. These maxima were derived from CRW's operational twice-weekly near-real-time global 50 km satellite bleaching HotSpot product. The product highlights regions where the SST is currently warmer than the highest climatological monthly mean temperature (often referred to as the maximum monthly mean (MMM) SST climatology) for that area and quantifies the magnitude of the temperature departure. Detailed information on the twice-weekly near-real-time HotSpot product is available at CRW's bleaching HotSpot website.
NOAA Degree Heating Weeks
Displayed here are NOAA CRW's maximum coral bleaching Degree Heating Weeks (DHW) showing the most stressful condition experienced during a month or a year. They were derived from CRW's operational twice-weekly near-real-time global 50 km satellite Degree Heating Week product that accumulates any HotSpot values greater than or equal to one degree Celsius over a 12-week window. Coral bleaching is related to prolonged periods of thermal stress. CRW's near-real-time DHW shows how stressful the conditions have been for corals in the last three months. DHW is a cumulative measurement of the intensity and duration of thermal stress, and is expressed in the units of °C-weeks. A DHW of 2 is equivalent to two weeks of HotSpot at one degree Celsius or one week of HotSpot at two degrees. DHW over 4 has been shown to cause significant bleaching, and values over 8 can cause widespread bleaching and some mortality. Detailed information on the twice-weekly near-real-time Degree Heating Week product is available at CRW's bleaching DHW website.
NOAA Virtual Stations
NOAA Virtual Stations This data layer shows NOAA Coral Reef Watch (CRW) operational near-real-time satellite bleaching monitoring information for 24 selected coral reef locations around the world (formerly known as Bleaching Index sites). For each virtual station, CRW provides current information on bleaching alert level, DHW, HotSpot, SST, and SST anomaly, plus the maximum monthly mean (MMM) SST climatology value for that location. The data displayed here are updated twice a week on every Monday and Thursday morning (U.S. Eastern Time). To view the information, simply turn on the NOAA Virtual Stations layer then click on a NOAA logo marker. In the pop-up window, choose "NOAA Virtual Stations" as the Identified Layer.

The five alert levels of thermal stress are defined in terms of the HotSpot and DHW values:

Bleaching Alert LevelDefinition
No Stress HotSpot <= 0
Bleaching Watch0 < HotSpot < 1
Bleaching Warning1 <= HotSpot and 0 < DHW < 4
Bleaching Alert Level 11 <= HotSpot and 4 <= DHW < 8
Bleaching Alert Level 21 <= HotSpot and 8 <= DHW

For details, please see CRW's Virtual Stations webpage. Subscription is available for free automatic Satellite Bleaching Alert emails on the bleaching thermal stress for these sites. More sites are expected to be added to the list in the near future.
Physical Features
Place Names
Place Names A list of reef-relevant place names was compiled by ReefBase. This list inlcludes: cities, towns, bays, straits, coral reefs, dive sites and other types of locations, and was compiled using a variety of sources.
Countries
Countries The country data layer originally comes from the Vector Map (VMap) Level 0, by the National Imagery and Mapping Agency (NIMA). Vector Map (VMap) Level 0 is an updated and improved version of the Digital Chart of the World (DCW®). The VMap Level 0 database provides worldwide coverage of vector-based geospatial data at 1:1,000,000 scale.
Topography
Topography Land topography data originates from the The Global Land One-kilometer Base Elevation (NOAA, NGDC: GLOBE) digital elevation model. It provides 30 arc second gridded elevation data at 1 km resolution. In ReefBase GIS, the topography-layer (as well as bathymetry) is turned off by default to improve performance. If you want to produce more visually attractive maps, you should click the "Show/Hide Topography" button in the map. For full metadata on GLOBE, please click here.
Bathymetry
The bathymetry (ocean depth) data originates from National Geophysical Data Center TerrainBase Global DTM Version 1.0. This data represent an estimate of depth for each 5-minute cell (~10km horizontal resolution). In ReefBase GIS, the bathymetry-layer (as well as topography) is turned off by default to improve performance. If you want to produce more visually attractive maps, you should click the "Show/Hide Topography" button in the map. For full details on TerrainBase, please click here.